Certain fuel rail assemblies for V-type engines comprise two main fuel rail tubes, one for each bank of cylinders, fluidly coupled by one or more cross-over tubes. When such main fuel rail tubes are rigid metal and such cross-over tubes are flexible synthetics, a common practice for connecting the cross-over tubes to the main fuel rail tubes is to attach metal nipples or hose barbs to the main fuel rail tubes and to push the ends of the cross-over tubes over the nipples or hose barbs in a telescopic manner. Because a hose barb is serrated, its serrations will embed themselves in the inner wall of the cross-over tube to seat and retain the cross-over tube in place. A retention band, of any conventional type, may be placed around the connection, as required.
When such main fuel rail tubes are rigid plastic, it becomes possible to form the nipples or hose barbs integrally therewith so that steps of separately fabricating the main fuel rails and the nipples or hose barbs and then assembling the nipples or hose barbs to the main fuel rails, can be avoided.
From the standpoint solely of hydraulic flow considerations, the cross sectional flow area through a nipple or hose barb and that through the cross-over tube connected to it can be equal. In reality however, they cannot be equal because the wall of the nipple or hose barb would otherwise have zero thickness. While the walls of the cross-over tube and of the nipple or hose barb must obviously have certain respective minimum thicknesses, the greater the sum of those thicknesses, the greater the disparity between the flow area through the nipple or hose barb on the one hand and the inside and outside diameters of the cross-over tube on the other hand. Thus, it becomes desirable to minimize the wall thicknesses of the nipple or hose barb and of the cross-over tube as much as possible, consistent with other design considerations and specifications.
Minimizing the wall thickness of a nipple or hose barb will, for a given wall thickness of the cross-over tube, minimize the amount of material required for the cross-over tube, and since the cross-over tube is apt to be considerably longer than the nipple or hose barb, material savings in the cross-over tube accrue by minimizing the wall thickness of the nipple or hose barb. However, too thin a wall for the nipple or hose barb, even if otherwise suitable for the fluid pressures involved, may not be sufficiently strong to withstand accidental, externally applied, side (lateral) impacts greater than a certain force magnitude, and therefore designing a nipple or hose barb so that it can withstand side impacts less than or equal to such a force magnitude will also cause an increase in the amount of material used in the cross-over tube.
The present invention relates to an improvement which is capable of providing protection for such a nipple or hose barb so that for side impact forces below a certain magnitude, the nipple or hose barb can be protected without the consequence of having to increase the size of the cross-over tube connected to it. Briefly, the invention comprises a guard wall that is integral with and projects from the plastic main fuel rail tube immediately adjacent the integral nipple or hose barb so as to laterally guard the nipple or hose guard. Thus, a lateral impact that would otherwise strike the nipple or hose barb will strike the guard wall instead, and so by making the guard wall to have sufficient strength to resist a certain magnitude of side impact force, the nipple or hose barb is thereby protected from such a blow. Indeed, the guard wall may be made substantially stronger than the wall of the nipple or hose barb.